CYP19A1 (aromatase) inhibitors, currently at their third generation, started to be used for breast cancer during the 80's of last century (Lønning and Eikesdal, 2013), and was followed by drugs able to target other enzymes (CYP11A1, CYP17A1, SRD5As; Table 3). Here, CYP19A1 is linked to breast cancer.